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قراءة كتاب Subspeciation in the Meadow Mouse, Microtus pennsylvanicus, in Wyoming, Colorado, and Adjacent Areas
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Subspeciation in the Meadow Mouse, Microtus pennsylvanicus, in Wyoming, Colorado, and Adjacent Areas
N. Amer. Fauna, 17:20, June 6, 1900.
Type.—Immature specimen (sex not specified), skin and skull, number of skin 594, number of skull 1717, deposited in the collections of the Smithsonian Institution, obtained by F. Kreutzfeldt, Sawatch Pass, Rocky Mountains [=Saguache Pass or Cochetopa Pass, Saguache County, Colorado], exact date unknown. I have not examined the type specimen.
Range.—Northern New Mexico, and southern Colorado (see list of specimens and Fig. 2).
Comparisons.—For comparison with the subspecies newly described below from northern Colorado see the account of that subspecies. The subspecies M. p. aztecus has been compared with M. p. modestus by Hall and Cockrum (1952:308) who reduced aztecus to subspecific rank. Although aztecus is separated by approximately 100 miles from modestus, and although no proof of intergradation is available, my studies of variation in this species lead me to agree with Hall and Cockrum that "the morphological differences between the two kinds of animals are of the degree and kind that separate subspecies, rather than species." A more adequate series of adults of aztecus is needed to clarify even the subspecific differences between aztecus and modestus.
Measurements.—Averages, extremes, and standard deviations of a number of series are included in Table 1 in order to facilitate comparisons between different subspecies.
Remarks.—The dividing line between M. p. modestus and the subspecies to the north on Figure 2 is drawn somewhat arbitrarily because few specimens are available from this area. Actual intergradation, in the form of a geographically intermediate population also morphologically intermediate between these two subspecies, is lacking. However, in most populations of both subspecies some individuals are intermediate between the two subspecies or even more like the other subspecies than the one to which they are referred. Warren (1942:226) states that modestus has been recorded from Lake County, although no reference to a specimen is given. Bailey (1900:21) cites Twin Lakes, in Lake County. That county is near the dividing line as I have drawn it, and therefore specimens from Lake County would be of special interest. An isolated colony of modestus occurs at San Rafael in Valencia County, New Mexico (Bailey, 1932:201). A hiatus of approximately 150 miles separates that colony from the southernmost locality shown in Figure 2. A single specimen, the skin of an immature Microtus without skull, from Trinchera, Colorado, taken by L. R. Hersey in 1912, is in the Colorado Museum of Natural History. No species of Microtine has been recorded from within 50 miles of this locality. The specimen is seemingly more like M. pennsylvanicus than any other species of Microtus. This locality is represented in Figure 2 by a question mark. Ecologically M. montanus fusus Hall and M. longicaudus mordax (Merriam) in the same region occupied by modestus seem to be more montane than modestus. It favors lush grass on the wet floors of alluvial valleys, and also irrigated areas such as that at Manassa.
Specimens examined.—Total 130. Colorado: Chaffee Co.: Salida, 3 (ERW). Saguache Co.: Monshower Meadows, 27 mi. NW Saguache [=3 mi. E Cochetopa Pass], 8 (USBS); Tevebaugh's Ranch, 20 mi. W Saguache, 46 (USBS, there are additional specimens not examined in detail by me); Cochetopa Pass, 33 mi. W Saguache, 1; 3 mi. N, 16 mi. W Saguache, 8500 ft., 5; 5 mi. NW Hooper, 1 (AMNH); Medano Ranch, 15 mi. NE Mosca, 2 (1 ERW, 1 USBS). Custer Co.: Westcliffe, 7800 ft., 1 (ERW). Alamosa Co.: Hooper, 10 (2 AMNH, 8 Denv); Mosca, 3 (ERW). Conejos Co.: 1½ mi. E Manassa, 11. Costilla Co.: Alamosa, 3 (Mich); 2 mi. S Blanca, 7800 ft., 6 (MVZ). New Mexico: Taos Co.: Arroyo Hondo, 7600 ft., 6 (USBS); Taos, Pueblo, 1 (USNM). Colfax Co.: 1 mi. S, 2 mi. E Eagle Nest, 8100 ft., 21; Taos Mountains, east slope, 8800 ft., 1 (USBS); Coyote Creek, 1 (USBS).
Microtus pennsylvanicus uligocola new subspecies
Type.—Adult male, skin and skull, number 26898, University of Kansas, Museum of Natural History, obtained by James O. Lounquist, original number 349, 6 miles west and ½ mile south of Loveland, 5200 ft., Larimer Co., Colorado, on July 26, 1948.
Range.—Northern Colorado. See Figure 2 and list of specimens examined.
Diagnosis.—Entire animal and skull large; color average for the species, neither extremely pale or dark in summer pelage; molar tooth-row long; nasals narrow; maxillary septum large; first upper molar wide; anterior margin of zygomatic arch above infraorbital foramen not deeply indented; fenestrae in posterodorsal parts of squamosal bones relatively long; braincase not elongate; auditory bullae and meatus large.
Comparisons.—From M. p. modestus, M. p. uligocola differs as follows: averages paler; prelambdoidal breadth and alveolar length of molar tooth-row significantly greater. Six pairs of skulls were compared. Of the features listed above under the "method of pairs" only two features differed in more than 75 per cent of the pairs; in 5 of 6 pairs uligocola had a less distinctly indented anterior margin of the zygomatic arch (Confidence Limit .95) and a more elongate posterodorsal squamosal fenestra (C. L. .85). Seven pairs of skulls from Boulder, Colorado, representing uligocola and from Colfax County, New Mexico, representing modestus differed in more than 75 per cent of the pairs in three features. Only one of these differences, the elongation of the posterodorsal squamosal fenestra, was the same as a difference noted above between topotypes of uligocola and modestus. A comparison of ten pairs of skulls of uligocola from Boulder, Colorado, and topotypes of uligocola revealed no significant differences. These observations are indicative of 1) the differences between samples and populations which may be assigned to a single subspecies, and 2) the fact that in general these local differences are less than the differences between subspecies. From insperatus, the subspecies to the north, uligocola differs as follows: darker in both summer and winter pelage; averaging larger in most measurements of the skull; significantly longer molar tooth-row; hind foot averaging longer. For comparisons with the subspecies to the east and the northwest see the accounts of those below.
Remarks.—M. p. uligocola is more closely restricted to wet situations than M. ochrogaster haydeni (Baird) whose general range lies to the eastward. The numerous lakes, the continuous supply of water from the mountains, and the irrigation systems at lower altitudes along the eastern base of the mountains provide the conditions to which uligocola is suited. It is named for its predilection for water.
The variability in color is relatively greater in topotypes of both uligocola and of modestus than in many of the other series studied. Specimens from Denver and Colorado Springs taken in late autumn and winter (October to February) are paler, more reddish and less blackish, than specimens taken in June and July at Loveland. This reddishness results from longer, and more intensely reddish tips of the hair. The entire hairs also are longer. The average weight of 16 adults (12 males and 4 non-pregnant females) from near Loveland is 49.7 gms. The average length of the ear is 13.4.
Specimens examined.—Total 228. Colorado: Larimer Co.: 6 mi. W, ½ mi. S